In the waning days of World War I, the United States invaded Russia. The mostly unknown story of this endeavor is the subject of James Carl Nelson’s “The Polar Bear Expedition.”

Nelson has an award-winning pedigree and a career of books under his belt on forgotten pieces of U.S. military history. This shines throughout the book but particularly in capturing the brutal nature of day-to-day combat. He does not shield readers from disturbing details. The specifics of who was shot where — limbs, head, heart — and the immediate physical consequences of it are abundant and difficult to forget. Although this means that “The Polar Bear Expedition” is not for the faint of heart, it serves as a stark reminder of the routine horror of war.

This is not simply because Nelson prefers the aesthetic. A major recurring theme in the book is the dubious justification for the 339th Regiment’s deployment. A large portion of its time in Russia comes after the armistice that ended World War I. The initial reason for being sent there was to reopen the eastern front against Germany while also aiding anti-Bolshevik forces that continued to fight against the Russian army.

With World War I over, harsh weather guaranteed and a formidable Red Army continuing to fight against them, their purpose was often obscured. “[The] fighting men would one day — if they were lucky — leave Russia still asking themselves … ‘Why did we go to Russia?’ ” Nelson writes.

This, in concert with the hard-to-handle images, is a haunting picture. Although Nelson begins the book by writing that “it seems the past will always be prologue when it comes to the United States and Russia,” “The Polar Bear Expedition” also feels like an illuminating book when considering the United States’ current presence in the Middle East. The question of why soldiers had to stay there, not to mention if their deployment in the first place was really necessary, is not rhetorical and is nonetheless never satisfyingly answered by anyone with power. Then and now, Nelson’s book makes clear, that’s not acceptable. It’s necessary to consider that war, to those fighting it, is not abstract.

“The Polar Bear Expedition” is careful to give full lives to its American subjects, referencing by name the family members and opportunities they left behind. The book’s largest flaw is its failure to do this for the Russian counterparts, referred to throughout as “Bolos” or “the enemy.” One does not have to be sympathetic to the Bolshevik cause to recognize that the men who made up the Red Army were fighting back against an invasion of their own country, and may have been as ambivalent as some in the 339th Regiment were.

The Polar Bear Expedition, by James Carl Nelson

Despite this, “The Polar Bear Expedition” is a fascinating, vivid exploration of an erased moment of U.S. military history. Nelson tackles the material with expertise and clarity.

Bradley Babendir has written for the New Republic, Pacific Standard, the New Inquiry and other publications.

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